Lee,
Could you please clarify "cooling side of the profile"? I have always thought of the reflow process in the same way as the wave process. During wave soldering, once a board exits the soldering area it begins a rapid descent back to room temp. Why would reflow soldering need to be any different after the relow zone? Is it related to flux residues?
Thanks,
Larry Davis
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee Whiteman
Sent: Monday, July 18, 2005 3:26 PM
To: [log in to unmask]
Subject: Re: [TN] Lead free oven
David,
I fooled around with reflow soldering ovens with between 3 and 5 zones.
The good news is that they were able to reflow solder Lead Free hardware, reaching the peak temperature of about 240C.
The bad news is that the profiles were very steep. In my opinion, in a production environment, the already smaller window for processing Lead Free solders will be reduced because the profiles will be too steep, thus exhausting the fluxes (which are manufacturer dependent). In one case, I mimicked the solder paste manufacturer's recommended profile correctly, but the peak temperature was reached in zone 4 of a 5 zone oven - messing up the cooling side of the profile.
The deltas across the board were similar to SnPb, but I was not comfortable with the results. In addition, depending upon the quality (solderability, thermal mass) of the materials (boards, components, solder paste) you will be running, your oven may not be as flexible or as forgiving as you may want.
In a prototype shop, where I was building very low volumes, I would run with it. In production, I want better control to account for boards and components that are less than optimum. Therefore I would consider getting an oven with a minimum of 7 zones.
For example, in one shop I went to, they had a 10 zone oven. They generated the thermal profile and built Lead Free soldered hardware with
SAC-305 with no problems. I have a 7 zone oven in my shop and we run SnPb and Lead Free hardware of varying thermal masses and geometries fine. For additional details, give me a call off-line.
Hope this helps.
Good Luck.
Lee Whiteman
Senior Manufacturing Engineer
American Competitiveness Institute
E-Mail: [log in to unmask]
Ph: (610) 362-1200 x208
Fax: (610) 362-1290
This message is for informational purposes only and does not supersede, modify, or create any agreements with ACI. Information contained in this message does not bind ACI or its affiliates to any commitment, either express or implied, unless ratified in writing by an authorized representative.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Tremmel
Sent: Monday, July 18, 2005 5:00 PM
To: [log in to unmask]
Subject: [TN] Lead free oven
Hello all,
We have a reflow oven with 4 zones and is capable of a maximum temperature setting of 500°C. We will probably be reflowing lead-free assemblies in the future and I would like some feedback as to whether or not our oven could be used for such a purpose.
My concern is not having enough zones to provide the controlled temperature deltas needed but also allowing proper flux activation.
As always, I appreciate whatever feedback I receive.
David Tremel
_________________________________________________________________
Consigue aquí las mejores y mas recientes ofertas de trabajo EE.UU.
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